public ShipmentTypeDto PutShipmentType(
            Guid key,
            ShipmentTypeRequestModel requestModel) {

            var shipmentType = _shipmentService.GetShipmentType(key);
            if (shipmentType == null) {

                throw new HttpResponseException(HttpStatusCode.NotFound);
            }

            var updatedShipmentType = _shipmentService.UpdateShipmentType(
                requestModel.ToShipmentType(shipmentType));

            return updatedShipmentType.ToShipmentTypeDto();
        }
        public HttpResponseMessage PostShipmentType(
            ShipmentTypeRequestModel requestModel) {

            var createdShipmentTypeResult = _shipmentService
                .AddShipmentType(requestModel.ToShipmentType());

            if (!createdShipmentTypeResult.IsSuccess) {

                return new HttpResponseMessage(HttpStatusCode.Conflict);
            }

            var response = Request.CreateResponse(HttpStatusCode.Created,
                createdShipmentTypeResult.Entity.ToShipmentTypeDto());

            response.Headers.Location = new Uri(Url.Link("DefaultHttpRoute",
                    new { key = createdShipmentTypeResult.Entity.Key }));

            return response;
        }